Patchwork [U-Boot,RFC,42/44] image: Add support for signing of FIT configurations

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Submitter Simon Glass
Date Jan. 5, 2013, 1:52 a.m.
Message ID <1357350734-13737-43-git-send-email-sjg@chromium.org>
Download mbox | patch
Permalink /patch/209637/
State Superseded, archived
Headers show

Comments

Simon Glass - Jan. 5, 2013, 1:52 a.m.
While signing images is useful, it does not provide complete protection
against several types of attack. For example, it it possible to create a
FIT with the same signed images, but with the configuration changed such
that a different one is selected (mix and match attack). It is also possible
to substitute a signed image from an older FIT version into a newer FIT
(roll-back attack).

Add support for signing of FIT configurations using the libfdt's region
support.

Please see doc/uImage.FIT/signature.txt for more information.

Signed-off-by: Simon Glass <sjg@chromium.org>
---
 common/cmd_bootm.c              |   12 ++
 common/image-sig.c              |  212 +++++++++++++++++++++++-
 doc/uImage.FIT/sign-configs.its |   45 +++++
 doc/uImage.FIT/signature.txt    |  167 ++++++++++++++++++-
 include/image.h                 |   15 ++
 tools/image-host.c              |  350 ++++++++++++++++++++++++++++++++++++++-
 6 files changed, 798 insertions(+), 3 deletions(-)
 create mode 100644 doc/uImage.FIT/sign-configs.its

Patch

diff --git a/common/cmd_bootm.c b/common/cmd_bootm.c
index cac9e53..d71ffb5 100644
--- a/common/cmd_bootm.c
+++ b/common/cmd_bootm.c
@@ -972,6 +972,18 @@  static const void *boot_get_kernel(cmd_tbl_t *cmdtp, int flag, int argc,
 								NULL);
 			printf("   Using '%s' configuration\n",
 				images->fit_uname_cfg);
+			if (IMAGE_ENABLE_VERIFY && images->verify) {
+				puts("   Verifying Hash Integrity ... ");
+				if (!fit_config_verify(fit_hdr,
+						cfg_noffset)) {
+					puts("Bad Data Hash\n");
+					bootstage_error(
+						BOOTSTAGE_ID_FIT_CHECK_HASH);
+					return NULL;
+				}
+				puts("OK\n");
+			}
+
 			bootstage_mark(BOOTSTAGE_ID_FIT_CONFIG);
 
 			os_noffset = fit_conf_get_kernel_node(fit_hdr,
diff --git a/common/image-sig.c b/common/image-sig.c
index c74d2f4..cfbb6ed 100644
--- a/common/image-sig.c
+++ b/common/image-sig.c
@@ -25,7 +25,6 @@ 
 #include <malloc.h>
 DECLARE_GLOBAL_DATA_PTR;
 #endif /* !USE_HOSTCC*/
-#include <errno.h>
 #include <image.h>
 #include <rsa.h>
 
@@ -50,6 +49,27 @@  struct image_sig_algo *image_get_sig_algo(const char *name)
 	return NULL;
 }
 
+struct image_region *fit_region_make_list(const void *fit,
+		struct fdt_region *fdt_regions, int count)
+{
+	struct image_region *region;
+	int i;
+
+	debug("Hash regions:\n");
+	debug("%10s %10s\n", "Offset", "Size");
+	region = calloc(sizeof(*region), count);
+	if (!region)
+		return NULL;
+	for (i = 0; i < count; i++) {
+		debug("%10x %10x\n", fdt_regions[i].offset,
+		      fdt_regions[i].size);
+		region[i].data = fit + fdt_regions[i].offset;
+		region[i].size = fdt_regions[i].size;
+	}
+
+	return region;
+}
+
 static int fit_image_setup_verify(struct image_sign_info *info,
 		const void *fit, int noffset, int required_keynode,
 		char **err_msgp)
@@ -195,3 +215,193 @@  int fit_image_verify_required_sigs(const void *fit, int image_noffset,
 
 	return 0;
 }
+
+int fit_config_check_sig(const void *fit, int noffset, int required_keynode,
+			 char **err_msgp)
+{
+	char * const exc_prop[] = {"data"};
+	struct fdt_region *fdt_regions;
+	const char *prop, *end, *name;
+	struct image_sign_info info;
+	struct image_region *region;
+	const uint32_t *strings;
+	uint8_t *fit_value;
+	int fit_value_len;
+	int max_regions;
+	char **node_inc;
+	int i, prop_len;
+	char path[200];
+	int count;
+
+	debug("%s: fdt=%p, conf='%s', sig='%s'\n", __func__, gd_fdt_blob(),
+	      fit_get_name(fit, noffset, NULL),
+	      fit_get_name(gd_fdt_blob(), required_keynode, NULL));
+	*err_msgp = NULL;
+	if (fit_image_setup_verify(&info, fit, noffset, required_keynode,
+			err_msgp))
+		return -1;
+
+	if (fit_image_hash_get_value(fit, noffset, &fit_value,
+					&fit_value_len)) {
+		*err_msgp = "Can't get hash value property";
+		return -1;
+	}
+
+	/* Count the number of strings in the property */
+	prop = fdt_getprop(fit, noffset, "hashed-nodes", &prop_len);
+	end = prop ? prop + prop_len : prop;
+	for (name = prop, count = 0; name < end; name++)
+		if (!*name)
+			count++;
+	if (!count) {
+		*err_msgp = "Can't get hashed-nodes property";
+		return -1;
+	}
+
+	/* Create a list of node names from those strings */
+	node_inc = calloc(sizeof(char *), count);
+	if (!node_inc) {
+		*err_msgp = "Out of memory for include node list";
+		return -1;
+	}
+	debug("Hash nodes (%d):\n", count);
+	for (name = prop, i = 0; name < end; name += strlen(name) + 1, i++) {
+		debug("   '%s'\n", name);
+		node_inc[i] = (char *)name;
+	}
+
+	/*
+	 * Each node can generate one region for each sub-node. Allow for
+	 * 7 sub-nodes (hash@1, signature@1, etc.) and some extra.
+	 */
+	max_regions = 20 + count * 7;
+	fdt_regions = calloc(sizeof(*fdt_regions), max_regions);
+	if (!fdt_regions) {
+		*err_msgp = "Out of memory for fdt hash regions";
+		return -1;
+	}
+
+	/* Get a list of regions to hash */
+	count = fdt_find_regions(fit, node_inc, count,
+			exc_prop, ARRAY_SIZE(exc_prop),
+			fdt_regions, max_regions - 1,
+			path, sizeof(path), 0);
+	if (count < 0) {
+		*err_msgp = "Failed to hash configuration";
+		return -1;
+	}
+	if (count == 0) {
+		*err_msgp = "No data to hash";
+		return -1;
+	}
+	if (count == max_regions - 1) {
+		*err_msgp = "Too many hash regions";
+		return -1;
+	}
+
+	/* Add the strings */
+	strings = fdt_getprop(fit, noffset, "hashed-strings", NULL);
+	if (strings) {
+		fdt_regions[count].offset = fdt_off_dt_strings(fit) +
+				fdt32_to_cpu(strings[0]);
+		fdt_regions[count].size = fdt32_to_cpu(strings[1]);
+		count++;
+	}
+
+	region = fit_region_make_list(fit, fdt_regions, count);
+	free(fdt_regions);
+
+	if (info.algo->verify(&info, region, count, fit_value, fit_value_len)) {
+		*err_msgp = "Verification failed";
+		return -1;
+	}
+
+	return 0;
+}
+
+static int fit_config_verify_sig(const void *fit, int conf_noffset,
+		const void *sig_blob, int sig_offset)
+{
+	int noffset;
+	int ndepth;
+	char *err_msg = "";
+	int verified = 0;
+	int ret;
+
+	/* Process all hash subnodes of the component conf node */
+	for (ndepth = 0,
+			noffset = fdt_next_subnode(fit, conf_noffset, &ndepth);
+			noffset >= 0;
+			noffset = fdt_next_subnode(fit, noffset, &ndepth)) {
+		const char *name = fit_get_name(fit, noffset, NULL);
+
+		if (!strncmp(name, FIT_SIG_NODENAME,
+				strlen(FIT_SIG_NODENAME))) {
+			ret = fit_config_check_sig(fit, noffset, sig_offset,
+						   &err_msg);
+			if (ret) {
+				puts("- ");
+			} else {
+				puts("+ ");
+				verified = 1;
+				break;
+			}
+		}
+	}
+
+	if (noffset == -FDT_ERR_TRUNCATED || noffset == -FDT_ERR_BADSTRUCTURE) {
+		err_msg = "Corrupted or truncated tree";
+		goto error;
+	}
+
+	return verified ? 0 : -EPERM;
+
+error:
+	printf(" error!\n%s for '%s' hash node in '%s' config node\n",
+			err_msg, fit_get_name(fit, noffset, NULL),
+			fit_get_name(fit, conf_noffset, NULL));
+	return -1;
+}
+
+int fit_config_verify_required_sigs(const void *fit, int conf_noffset,
+		const void *sig_blob)
+{
+	int ndepth, noffset;
+	int sig_node;
+
+	/* Work out what we need to verify */
+	sig_node = fdt_subnode_offset(sig_blob, 0, FIT_SIG_NODENAME);
+	if (sig_node < 0) {
+		debug("%s: No signature node found: %s\n", __func__,
+			fdt_strerror(sig_node));
+		return 0;
+	}
+
+	for (ndepth = 0, noffset = fdt_next_subnode(sig_blob, sig_node,
+						     &ndepth);
+			noffset >= 0;
+			noffset = fdt_next_subnode(sig_blob, noffset,
+						   &ndepth)) {
+		const char *required;
+		int ret;
+
+		required = fdt_getprop(sig_blob, noffset, "required", NULL);
+		if (!required || strcmp(required, "conf"))
+			continue;
+		ret = fit_config_verify_sig(fit, conf_noffset, sig_blob,
+					    noffset);
+		if (ret) {
+			printf("Failed to verify required signature '%s'\n",
+				fit_get_name(sig_blob, noffset, NULL));
+			return ret;
+		}
+	}
+
+	return 0;
+}
+
+int fit_config_verify(const void *fit, int conf_noffset)
+{
+	return !fit_config_verify_required_sigs(fit, conf_noffset,
+						gd_fdt_blob());
+}
diff --git a/doc/uImage.FIT/sign-configs.its b/doc/uImage.FIT/sign-configs.its
new file mode 100644
index 0000000..3c17f04
--- /dev/null
+++ b/doc/uImage.FIT/sign-configs.its
@@ -0,0 +1,45 @@ 
+/dts-v1/;
+
+/ {
+	description = "Chrome OS kernel image with one or more FDT blobs";
+	#address-cells = <1>;
+
+	images {
+		kernel@1 {
+			data = /incbin/("test-kernel.bin");
+			type = "kernel_noload";
+			arch = "sandbox";
+			os = "linux";
+			compression = "lzo";
+			load = <0x4>;
+			entry = <0x8>;
+			kernel-version = <1>;
+			hash@1 {
+				algo = "sha1";
+			};
+		};
+		fdt@1 {
+			description = "snow";
+			data = /incbin/("sandbox-kernel.dtb");
+			type = "flat_dt";
+			arch = "sandbox";
+			compression = "none";
+			fdt-version = <1>;
+			hash@1 {
+				algo = "sha1";
+			};
+		};
+	};
+	configurations {
+		default = "conf@1";
+		conf@1 {
+			kernel = "kernel@1";
+			fdt = "fdt@1";
+			signature@1 {
+				algo = "sha1,rsa2048";
+				key-name-hint = "dev";
+				sign-images = "fdt", "kernel";
+			};
+		};
+	};
+};
diff --git a/doc/uImage.FIT/signature.txt b/doc/uImage.FIT/signature.txt
index 48aa616..484d76d 100644
--- a/doc/uImage.FIT/signature.txt
+++ b/doc/uImage.FIT/signature.txt
@@ -105,8 +105,27 @@  When the image is signed, the following properties are optional:
 
 - comment: Additional information about the signer or image
 
+For config bindings (see Signed Configurations below), the following
+additional properties are optional:
 
-Example: See sign-images.its for an example image tree source file.
+- sign-images: A list of images to sign, each being a property of the conf
+node that contains then. The default is "kernel,fdt" which means that these
+two images will be looked up in the config and signed if present.
+
+For config bindings, these properties are added by the signer:
+
+- hashed-nodes: A list of nodes which were hashed by the signer. Each is
+	a string - the full path to node. A typical value might be:
+
+	hashed-nodes = "/", "/configurations/conf@1", "/images/kernel@1",
+		"/images/kernel@1/hash@1", "/images/fdt@1",
+		"/images/fdt@1/hash@1";
+
+- hashed-strings: The start and size of the string region of the FIT that
+	was hashed
+
+Example: See sign-images.its for an example image tree source file and
+sign-configs.its for config signing.
 
 
 Public Key Storage
@@ -144,6 +163,152 @@  For RSA the following are mandatory:
 - rsa,n0-inverse: -1 / modulus[0] mod 2^32
 
 
+Signed Configurations
+---------------------
+While signing images is useful, it does not provide complete protection
+against several types of attack. For example, it it possible to create a
+FIT with the same signed images, but with the configuration changed such
+that a different one is selected (mix and match attack). It is also possible
+to substitute a signed image from an older FIT version into a newer FIT
+(roll-back attack).
+
+As an example, consider this FIT:
+
+/ {
+	images {
+		kernel@1 {
+			data = <data for kernel1>
+			signature@1 {
+				algo = "sha1,rsa2048";
+				value = <kernel signature 1>
+			};
+		};
+		kernel@2 {
+			data = <data for kernel2>
+			signature@1 {
+				algo = "sha1,rsa2048";
+				value = <kernel signature 2>
+			};
+		};
+		fdt@1 {
+			data = <data for fdt1>;
+			signature@1 {
+				algo = "sha1,rsa2048";
+				vaue = <fdt signature 1>
+			};
+		};
+		fdt@2 {
+			data = <data for fdt2>;
+			signature@1 {
+				algo = "sha1,rsa2048";
+				vaue = <fdt signature 2>
+			};
+		};
+	};
+	configurations {
+		default = "conf@1";
+		conf@1 {
+			kernel = "kernel@1";
+			fdt = "fdt@1";
+		};
+		conf@1 {
+			kernel = "kernel@2";
+			fdt = "fdt@2";
+		};
+	};
+};
+
+Since both kernels are signed it is easy for an attacker to add a new
+configuration 3 with kernel 1 and fdt 2:
+
+	configurations {
+		default = "conf@1";
+		conf@1 {
+			kernel = "kernel@1";
+			fdt = "fdt@1";
+		};
+		conf@1 {
+			kernel = "kernel@2";
+			fdt = "fdt@2";
+		};
+		conf@3 {
+			kernel = "kernel@1";
+			fdt = "fdt@2";
+		};
+	};
+
+With signed images, nothing protects against this. Whether it gains an
+advantage for the attacker is debatable, but it is not secure.
+
+To solved this problem, we support signed configurations. In this case it
+is the configurations that are signed, not the image. Each image has its
+own hash, and we include the hash in the configuration signature.
+
+So the above example is adjusted to look like this:
+
+/ {
+	images {
+		kernel@1 {
+			data = <data for kernel1>
+			hash@1 {
+				algo = "sha1";
+				value = <kernel hash 1>
+			};
+		};
+		kernel@2 {
+			data = <data for kernel2>
+			hash@1 {
+				algo = "sha1";
+				value = <kernel hash 2>
+			};
+		};
+		fdt@1 {
+			data = <data for fdt1>;
+			hash@1 {
+				algo = "sha1";
+				value = <fdt hash 1>
+			};
+		};
+		fdt@2 {
+			data = <data for fdt2>;
+			hash@1 {
+				algo = "sha1";
+				value = <fdt hash 2>
+			};
+		};
+	};
+	configurations {
+		default = "conf@1";
+		conf@1 {
+			kernel = "kernel@1";
+			fdt = "fdt@1";
+			signature@1 {
+				algo = "sha1,rsa2048";
+				value = <conf 1 signature>;
+			};
+		};
+		conf@2 {
+			kernel = "kernel@2";
+			fdt = "fdt@2";
+			signature@1 {
+				algo = "sha1,rsa2048";
+				value = <conf 1 signature>;
+			};
+		};
+	};
+};
+
+
+You can see that we have added hashes for all images (since they are no
+longer signed), and a signature to each configuration. In the above example,
+mkimage will sign configurations/conf@1, the kernel and fdt that are
+pointed to by the configuration (/images/kernel@1, /images/kernel@1/hash@1,
+/images/fdt@1, /images/fdt@1/hash@1) and the root structure of the image
+(so that it isn't possible to add or remove root nodes). The signature is
+written into /configurations/conf@1/signature@1/value. It can easily be
+verified later even if the FIT has signed with other keys in the meantime.
+
+
 Verification
 ------------
 FITs are verified when loaded. After the configuration is selected a list
diff --git a/include/image.h b/include/image.h
index b8aea83..ad3e4b8 100644
--- a/include/image.h
+++ b/include/image.h
@@ -633,6 +633,7 @@  int fit_add_verification_data(const char *keydir, void *keydest, void *fit,
 			      const char *comment, int require_keys);
 
 int fit_image_verify(const void *fit, int noffset);
+int fit_config_verify(const void *fit, int conf_noffset);
 int fit_all_image_verify(const void *fit);
 int fit_image_check_os(const void *fit, int noffset, uint8_t os);
 int fit_image_check_arch(const void *fit, int noffset, uint8_t arch);
@@ -801,6 +802,20 @@  int fit_image_verify_required_sigs(const void *fit, int image_noffset,
 int fit_image_check_sig(const void *fit, int noffset, const void *data,
 		size_t size, int required_keynode, char **err_msgp);
 
+/**
+ * fit_region_make_list() - Make a list of regions to hash
+ *
+ * Given a list of FIT regions (offset, size) provided by libfdt, create
+ * a list of regions (void *, size) for use by the signature creationg
+ * and verification code.
+ *
+ * @fit:		FIT image to process
+ * @fdt_regions:	Regions as returned by libfdt
+ * @count:		Number of regions returned by libfdt
+ * @return pointer to list of regions, or NULL if out of memory
+ */
+struct image_region *fit_region_make_list(const void *fit,
+		struct fdt_region *fdt_regions, int count);
 
 #ifndef USE_HOSTCC
 static inline int fit_image_check_target_arch(const void *fdt, int node)
diff --git a/tools/image-host.c b/tools/image-host.c
index 4196190..8304253 100644
--- a/tools/image-host.c
+++ b/tools/image-host.c
@@ -343,10 +343,335 @@  int fit_image_add_verification_data(const char *keydir, void *keydest,
 	return 0;
 }
 
+struct strlist {
+	int count;
+	char **strings;
+};
+
+static void strlist_init(struct strlist *list)
+{
+	memset(list, '\0', sizeof(*list));
+}
+
+static void strlist_free(struct strlist *list)
+{
+	int i;
+
+	for (i = 0; i < list->count; i++)
+		free(list->strings[i]);
+	free(list->strings);
+}
+
+static int strlist_add(struct strlist *list, const char *str)
+{
+	char *dup;
+
+	dup = strdup(str);
+	list->strings = realloc(list->strings,
+				(list->count + 1) * sizeof(char *));
+	if (!list || !str)
+		return -1;
+	list->strings[list->count++] = dup;
+
+	return 0;
+}
+
+static const char *fit_config_get_image_list(void *fit, int noffset,
+		int *lenp, int *allow_missingp)
+{
+	static const char default_list[] = FIT_KERNEL_PROP "\0"
+			FIT_FDT_PROP;
+	const char *prop;
+
+	/* If there is an "image" property, use that */
+	prop = fdt_getprop(fit, noffset, "sign-images", lenp);
+	if (prop) {
+		*allow_missingp = 0;
+		return *lenp ? prop : NULL;
+	}
+
+	/* Default image list */
+	*allow_missingp = 1;
+	*lenp = sizeof(default_list);
+
+	return default_list;
+}
+
+static int fit_config_get_hash_list(void *fit, int conf_noffset,
+				    int sig_offset, struct strlist *node_inc)
+{
+	int allow_missing;
+	const char *prop, *iname, *end;
+	const char *conf_name, *sig_name;
+	char name[200], path[200];
+	int image_count;
+	int ret, len;
+
+	conf_name = fit_get_name(fit, conf_noffset, NULL);
+	sig_name = fit_get_name(fit, sig_offset, NULL);
+
+	/*
+	 * Build a list of nodes we need to hash. We always need the root
+	 * node and the configuration.
+	 */
+	strlist_init(node_inc);
+	snprintf(name, sizeof(name), "%s/%s", FIT_CONFS_PATH, conf_name);
+	if (strlist_add(node_inc, "/") ||
+			strlist_add(node_inc, name))
+		goto err_mem;
+
+	/* Get a list of images that we intend to sign */
+	prop = fit_config_get_image_list(fit, conf_noffset, &len,
+					&allow_missing);
+	if (!prop)
+		return 0;
+
+	/* Locate the images */
+	end = prop + len;
+	image_count = 0;
+	for (iname = prop; iname < end; iname += strlen(iname) + 1) {
+		int ndepth, noffset;
+		int image_noffset;
+		int hash_count;
+
+		image_noffset = fit_conf_get_prop_node(fit, conf_noffset,
+						       iname);
+		if (image_noffset < 0) {
+			printf("Failed to find image '%s' in"
+				" configuration '%s/%s'\n", iname, conf_name,
+				sig_name);
+			if (allow_missing)
+				continue;
+
+			return -ENOENT;
+		}
+
+		ret = fdt_get_path(fit, image_noffset, path, sizeof(path));
+		if (ret < 0)
+			goto err_path;
+		if (strlist_add(node_inc, path))
+			goto err_mem;
+
+		snprintf(name, sizeof(name), "%s/%s", FIT_CONFS_PATH,
+			 conf_name);
+
+		/* Add all this image's hashes */
+		hash_count = 0;
+		for (ndepth = 0,
+			noffset = fdt_next_subnode(fit, image_noffset, &ndepth);
+			noffset >= 0;
+			noffset = fdt_next_subnode(fit, noffset, &ndepth)) {
+			const char *name = fit_get_name(fit, noffset, NULL);
+
+			if (strncmp(name, FIT_HASH_NODENAME,
+					strlen(FIT_HASH_NODENAME)))
+				continue;
+			ret = fdt_get_path(fit, noffset, path, sizeof(path));
+			if (ret < 0)
+				goto err_path;
+			if (strlist_add(node_inc, path))
+				goto err_mem;
+			hash_count++;
+		}
+
+		if (!hash_count) {
+			printf("Failed to find any hash nodes in configuration"
+				" '%s/%s' image '%s' - without these it is"
+				" not possible to verify this image\n",
+				conf_name, sig_name, iname);
+			return -ENOMSG;
+		}
+
+		image_count++;
+	}
+
+	if (!image_count) {
+		printf("Failed to find any images for configuration '%s/%s'\n",
+		       conf_name, sig_name);
+		return -ENOMSG;
+	}
+
+	return 0;
+
+err_mem:
+	printf("Out of memory processing configuration '%s/%s'\n", conf_name,
+		sig_name);
+	return -ENOMEM;
+
+err_path:
+	printf("Failed to get path for image '%s' in"
+		" configuration '%s/%s': %s\n", iname, conf_name, sig_name,
+		fdt_strerror(ret));
+	return -ENOENT;
+}
+
+static int fit_config_get_data(void *fit, int conf_noffset, int noffset,
+		struct image_region **regionp, int *region_countp,
+		char **region_propp, int *region_proplen)
+{
+	char * const exc_prop[] = {"data"};
+	struct strlist node_inc;
+	struct image_region *region;
+	struct fdt_region fdt_regions[100];
+	const char *conf_name, *sig_name;
+	char path[200];
+	int count, i;
+	char *region_prop;
+	int ret, len;
+
+	conf_name = fit_get_name(fit, conf_noffset, NULL);
+	sig_name = fit_get_name(fit, conf_noffset, NULL);
+	debug("%s: conf='%s', sig='%s'\n", __func__, conf_name, sig_name);
+
+	/* Get a list of nodes we want to hash */
+	ret = fit_config_get_hash_list(fit, conf_noffset, noffset, &node_inc);
+	if (ret)
+		return ret;
+
+	/* Get a list of regions to hash */
+	count = fdt_find_regions(fit, node_inc.strings, node_inc.count,
+			exc_prop, ARRAY_SIZE(exc_prop),
+			fdt_regions, ARRAY_SIZE(fdt_regions),
+			path, sizeof(path), 1);
+	if (count < 0) {
+		printf("Failed to hash configuration '%s/%s': %s\n", conf_name,
+		       sig_name, fdt_strerror(ret));
+		return -EIO;
+	}
+	if (count == 0) {
+		printf("No data to hash for configuration '%s/%s': %s\n",
+		       conf_name, sig_name, fdt_strerror(ret));
+		return -EINVAL;
+	}
+
+	/* Build our list of data blocks */
+	region = fit_region_make_list(fit, fdt_regions, count);
+	if (!region) {
+		printf("Out of memory hashing configuration '%s/%s'\n",
+		       conf_name, sig_name);
+		return -ENOMEM;
+	}
+
+	/* Create a list of all hashed properties */
+	debug("Hash nodes:\n");
+	for (i = len = 0; i < node_inc.count; i++) {
+		debug("   %s\n", node_inc.strings[i]);
+		len += strlen(node_inc.strings[i]) + 1;
+	}
+	region_prop = malloc(len);
+	if (!region_prop) {
+		printf("Out of memory setting up regions for"
+			" configuration '%s/%s'\n", conf_name, sig_name);
+		return -ENOMEM;
+	}
+	for (i = len = 0; i < node_inc.count;
+			len += strlen(node_inc.strings[i]) + 1, i++)
+		strcpy(region_prop + len, node_inc.strings[i]);
+	strlist_free(&node_inc);
+
+	*region_countp = count;
+	*regionp = region;
+	*region_propp = region_prop;
+	*region_proplen = len;
+
+	return 0;
+}
+
+static int fit_config_process_sig(const char *keydir, void *keydest,
+		void *fit, const char *conf_name, int conf_noffset,
+		int noffset, const char *comment, int require_keys)
+{
+	struct image_sign_info info;
+	const char *node_name;
+	struct image_region *region;
+	char *region_prop;
+	int region_proplen;
+	int region_count;
+	uint8_t *value;
+	uint value_len;
+	int ret;
+
+	node_name = fit_get_name(fit, noffset, NULL);
+	if (fit_config_get_data(fit, conf_noffset, noffset, &region,
+			&region_count, &region_prop, &region_proplen))
+		return -1;
+
+	if (fit_image_setup_sig(&info, keydir, fit, conf_name, noffset,
+			require_keys ? "conf" : NULL))
+		return -1;
+
+	ret = info.algo->sign(&info, region, region_count, &value, &value_len);
+	free(region);
+	if (ret) {
+		printf("Failed to sign '%s' signature node in '%s'"
+			" conf node\n", node_name, conf_name);
+
+		/* We allow keys to be missing */
+		if (ret == -ENOENT)
+			return 0;
+		return -1;
+	}
+
+	if (fit_image_write_sig(fit, noffset, value, value_len, comment,
+				region_prop, region_proplen)) {
+		printf("Can't write signature for "
+			"'%s' signature node in '%s' conf node\n",
+			node_name, conf_name);
+		return -1;
+	}
+	free(value);
+	free(region_prop);
+
+	/* Get keyname again, as FDT has changed and invalidated our pointer */
+	info.keyname = fdt_getprop(fit, noffset, "key-name-hint", NULL);
+
+	/* Write the public key into the supplied FDT file */
+	if (keydest && info.algo->add_verify_data(&info, keydest)) {
+		printf("Failed to add verification data for "
+			"'%s' signature node in '%s' image node\n",
+			node_name, conf_name);
+		return -1;
+	}
+
+	return 0;
+}
+
+static int fit_config_add_verification_data(const char *keydir, void *keydest,
+		void *fit, int conf_noffset, const char *comment,
+		int require_keys)
+{
+	const char *conf_name;
+	int noffset;
+	int ndepth;
+
+	conf_name = fit_get_name(fit, conf_noffset, NULL);
+
+	/* Process all hash subnodes of the configuration node */
+	for (ndepth = 0,
+			noffset = fdt_next_subnode(fit, conf_noffset, &ndepth);
+			noffset >= 0;
+			noffset = fdt_next_subnode(fit, noffset, &ndepth)) {
+		const char *node_name;
+		int ret = 0;
+
+		node_name = fit_get_name(fit, noffset, NULL);
+		if (!strncmp(node_name, FIT_SIG_NODENAME,
+				strlen(FIT_SIG_NODENAME))) {
+			ret = fit_config_process_sig(keydir, keydest,
+				fit, conf_name, conf_noffset, noffset, comment,
+				require_keys);
+		}
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
 int fit_add_verification_data(const char *keydir, void *keydest, void *fit,
 			      const char *comment, int require_keys)
 {
-	int images_noffset;
+	int images_noffset, confs_noffset;
 	int noffset;
 	int ndepth;
 	int ret;
@@ -375,5 +700,28 @@  int fit_add_verification_data(const char *keydir, void *keydest, void *fit,
 			return ret;
 	}
 
+	/* If there are no keys, we can't sign configurations */
+	if (!keydir)
+		return 0;
+
+	/* Find configurations parent node offset */
+	confs_noffset = fdt_path_offset(fit, FIT_CONFS_PATH);
+	if (confs_noffset < 0) {
+		printf("Can't find images parent node '%s' (%s)\n",
+			FIT_IMAGES_PATH, fdt_strerror(confs_noffset));
+		return -ENOENT;
+	}
+
+	/* Process its subnodes, print out component images details */
+	for (ndepth = 0,
+			noffset = fdt_next_subnode(fit, confs_noffset, &ndepth);
+			noffset >= 0;
+			noffset = fdt_next_subnode(fit, noffset, &ndepth)) {
+		ret = fit_config_add_verification_data(keydir, keydest,
+				fit, noffset, comment, require_keys);
+		if (ret)
+			return ret;
+	}
+
 	return 0;
 }